Electromechanical Switch for Controlling Toxic Gas

ABSTRACT

An electromechanical switch comprising a plunger, a first switch in contact with the plunger in a first position of the plunger, in which a connection of the switch is open, a button in sliding contact with the plunger, and a solenoid in contact with the plunger in a second position of the plunger, in which a connection of the first switch is closed.

TECHNICAL FIELD OF THE INVENTION

The present disclosures relate to a system and method of controlling theconcentrations of one or more gases in a space. More specifically, thepresent disclosure relates to a system and method for preventing andcontrolling the concentration of gaseous products or byproducts, such ascarbon monoxide (CO), in a space when a predetermined concentration isexceeded by interrupting the process, such as combustion, which producesthe gases.

BACKGROUND OF THE INVENTION

The combustion or processing of certain materials often results in theproduction of certain gases. When the concentration of these gasesexceeds a predetermined threshold, it may be desirable to cease thecombustion or processing which is directly or indirectly producing thegas. One such gas is carbon monoxide. Carbon monoxide is a colorless,odorless, tasteless gas, which is produced through an incompletecombustion of a hydrocarbon. Carbon monoxide can be produced by variousfuel burning appliances, such as, fuel fired furnaces, gas hot waterheaters, gas stoves, gas dryers, space heaters, vehicles, snow blowers,portable power generators, etc.

Once present, this gas circulates freely throughout a building, such asa home. If this gas is not ventilated properly, carbon monoxidepoisoning may result. Carbon monoxide inhibits the blood's ability tocarry oxygen to body tissue, including vital organs such as the heartand brain. When carbon monoxide is inhaled, it combines withoxygen-carrying hemoglobin of the blood to form carboxyhemoglobin. Oncecombined with the hemoglobin, the hemoglobin is no longer available fortransporting oxygen. The amount of carboxyhemoglobin that builds up is afactor of the concentration of the gas being inhaled and the duration ofthe exposure. Carbon monoxide can act in the body in highconcentrations, or slowly over a long period of time. Because it takesseveral hours to remove carbon monoxide from the body of a person,concentrations of carbon monoxide can gradually build up in the bloodcausing headaches, fatigue, dizziness, nausea, burning eyes, orunconsciousness.

Sources of Carbon Monoxide (CO)

Carbon monoxide can be produced whenever a hydrocarbon is burned and thecombustion is incomplete. Hydrocarbons include all fossil fuels andtheir derivations, such as oil, natural gas, gasoline, coal, etc.Sources of carbon monoxide include power generators and other gasolinepowered equipment; un-vented kerosene and gas space heaters; leakingchimneys and furnaces; back-drafting from furnaces, and others.Incomplete oxidation during combustion in gas ranges and non-vented gasor kerosene heaters may cause high concentrations of CO in indoor air.Worn or poorly adjusted and maintained combustion devices (e.g.,boilers, furnaces) can be significant sources of CO.

Standards or Guidelines

According to the inventor's understanding, no standards for COconcentration have been agreed upon for indoor air. However, COdetectors/alarms always have been and still are designed to alarm beforepotentially life-threatening levels of CO are reached. The UL standard2034 (1998 revision) has stricter requirements that the detector/alarmmust meet before it can sound. As a result, the possibility of nuisancealarms is decreased. UL-2034 standard calls for the following levels andactions:

70 PPM—alarm between 60 & 240 minutes150 PPM—alarm between 10 & 50 minutes400 PPM—alarm between 4 & 15 minutes

Carbon Monoxide (CO) Detectors

Because carbon monoxide is a colorless, odorless, tasteless gas, itvirtually impossible to detect its presence without a carbon monoxidedetector. Devices for sensing carbon monoxide and triggering an audibleand/or visual alarm in the presence of excess concentrations of carbonmonoxide are presently available and their use is known to those ofordinary skill in the art. The most common types of CO sensors used inCO detectors are described below.

A biomimetic type (chem-optical or gel cell) sensors works with a formof synthetic hemoglobin which darkens in the presence of CO, andlightens without it. This can either be seen directly or connected to alight sensor and alarm.

Electrochemical-type sensors are a type of fuel cell that, instead ofbeing designed to produce power, is designed to produce a current thatis precisely related to the amount of the target gas (in this casecarbon monoxide) in the atmosphere. Measurement of the current thereforegives a measure of the concentration of carbon monoxide in theatmosphere. Essentially the electrochemical cell consists of acontainer, 2 electrodes, connection wires and an electrolyte—typicallysulfuric acid. Carbon monoxide is oxidized at one electrode to carbondioxide whilst oxygen is consumed at the other electrode. For carbonmonoxide detection, the electrochemical cell has advantages over theother technologies in that it has a highly accurate and linear output tocarbon monoxide concentration, requires minimal power as it is operatedat room temperature, and has a long lifetime (typically commercialavailable cells now have lifetimes of 5 years or greater). Untilrecently, the cost of these cells and concerns about their long termreliability had limited uptake of this technology in the marketplacealthough these concerns are now largely overcome.

The electrochemical-type sensor type is the example used for explainingembodiments of the invention below. Typically the cell used generated acurrent of 45 nA/ppm (nano amperes per part per million of carbonmonoxide) for example, a concentration of 85 ppm in the area will createa current equal to (45 nA/ppm×85 ppm)=3.825 uA (micro Amperes). Thiscurrent can be easily converted to voltage by using a high precisionresistor, and then measured by an A/D (analog to digital) convertereither external to, or built in the microcontroller as explained below.

In a semiconductor-type detector, thin wires of the semiconductor tindioxide wafer on an insulating ceramic base provide a sensor monitoredby an integrated circuit. CO reduces resistance and so allows a greatercurrent which if high enough will lead to the monitor triggering analarm. This sensor is more expensive and less used in residential COdetectors.

Generators

In the majority of the portable gas powered generators available in theretail and commercial markets today, the mechanism used shorts one leadof the ignition module to ground (which is normally the generator'smetal frame and body of the alternator) in order to shut down the gasengine. This is true for both manually cranked gas engines (pull rope)and electrically cranked, larger engines (sealed lead acid batteries orelectric starter—such as of those used in larger generators and snowthrowers). For battery or electrically cranked engines, there are twoswitches, one mostly called RUN/STOP and the other for cranking theengine, normally a momentary pushbutton called START. There are certaingenerators and engines that both of these switches may be combined intoone, three position switch. The positions will then be STOP-RUN-START,being the START position a momentary position.

Microcontrollers

The term microcontroller as used herein includes microcontrollers,microprocessors, and the like. Microcontrollers are highly integrateddevices that execute a stored program. The program is stored as a seriesof instructions, usually in non-volatile memory. Microcontrollers oftenuse external resonators or crystals to supply clock pulses that pacesthe microcontroller. Instructions may take one, two, or more clockcycles to be executed depending on the design of the microcontroller.

SUMMARY

A safety system for connection to a toxic gas detector and a toxic gasproducing engine, and its operating method, includes an interrupt devicecoupled to connections to the detector and the engine. The interruptdevice includes a toxic gas signal detecting circuit and a circuit forpermitting starting of the engine. The detecting circuit activates thepermitting circuit if the toxic gas signal represents a toxic gasconcentration below a predetermined level. In one embodiment, thepermitting circuit is activated if the safety system is healthy andfully functional.

Similarly, a safety system for connection to a toxic gas detector and atoxic gas supply, and its operating method, includes an interrupt devicecoupled to connections to the detector and the toxic gas supply. Theinterrupt device includes a toxic gas signal detecting circuit and acircuit for permitting of flow from the toxic gas supply. The detectingcircuit activates the permitting circuit if the toxic gas signalrepresents a toxic gas concentration below a predetermined level.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the block diagram of a typical gas detection unit, in thisexample a typical CO detector.

FIG. 2 shows the different status indication on a detector having onelight emitting diode (LEDs).

FIG. 3 shows the different status indication on a detector having twolight emitting diodes (LEDs).

FIG. 4 shows the different status indication on a detector having threelight emitting diodes (LEDs).

FIG. 5 shows a gas detector with a plug in replaceable sensor.

FIG. 6 shows the signals used by embodiments of the invention tointerface to a commercial CO detector.

FIG. 7 shows a typical internal mains-powered power supply of acommercial CO detector.

FIG. 8 shows yet another typical internal mains-powered power supply ofa commercial CO detector.

FIG. 9 shows a block diagram of an embodiment of the invention.

FIG. 10 shows the interfacing signals to a portable gas generator.

FIG. 11 is a representation using an electromechanical relay and activelogic of an embodiment of the invention based on a 3V CO detector.

FIG. 12 is a representation using an electromechanical relay and activelogic of an embodiment of the invention based on a 9V CO detector.

FIG. 13 shows an implementation, using a commercial CO detector with asolid state relay, using any type of battery.

FIG. 14 shows an implementation using the microcontroller built inside acommercial CO detector.

FIG. 15 shows an implementation with a commercial mains-powered COdetector without a battery backup and electromechanical switch.

FIG. 16 shows a block diagram of an overall interface to a new orretrofitted portable power generator.

FIG. 17 shows a basic implementation of an embodiment of the inventionby using a simple commercial CO detector.

FIG. 18 shows a typical internal power supply of a CO detector used torecharge and in conjunction with rechargeable batteries.

FIG. 19 shows an implantation of a power switch which interrupts powerto the room or appliance when toxic gas is detected.

FIG. 20 shows an implementation with a commercial CO detector without abattery backup and with a special electromechanical switch.

FIG. 21 shows an electromechanical switch to be used in conjunction withthe safety device—in the STOP mode.

FIG. 22 shows the same electromechanical switch in the RUN position,prior to running the generator.

FIG. 23 shows the same electromechanical switch in the RUN position,with the generator running.

FIG. 24 shows a system for generating power for a safety device from themagneto of the ignition system of a gas engine.

FIG. 25 shows a safety device for alarming and controlling devices usingtanks of toxic gas such as a fossil fuel.

FIG. 26 shows an embodiment of the invention to control devices operatedby tanks of a toxic gas, such as a fossil fuel, using a commerciallyavailable CO detector.

DETAILED DESCRIPTION

There are reported and existing cases of people improperly operatingpower generators indoors without proper ventilation, which resulted infatalities. A method and device to detect dangerous levels of CO andeffectively shutdown the gas engine was developed, tested andsuccessfully installed in portable power generators which will remedythis situation.

Embodiments of the invention use a variety of methods to interface tothe gas engine without interfering with its normal operation, andwithout modifications to the engine, or alternator. This system monitorsthe emission of CO in the vicinity of the power generator. Once itdetects dangerous concentrations of CO, it effectively shuts down theengine. The engine cannot be restarted until the level of CO drops down.The preferred embodiment has the capability of minimizing falseshutdowns. Many scenarios were properly considered to encompass normaloperational ways of the power generators, while contemplating andunderstanding erroneous operations of the generator that may lead tolethal consequences. An audible alarm and visual alarm indicator(flasher) for the hearing impaired has been also incorporated in thepreferred embodiment. In addition to shutting down the appliance, boththese alarms will be set until they are manually silenced. In the courseof explaining embodiments of the invention, different ways to interfaceto different CO or commercial gas detectors are described. Thesedetectors are used as a building block for the detection of the toxicgases. There are many companies (for example Kiddie, First Alert, etc)with extensive expertise in minimizing false alarms, analyzing andproperly responding to different levels and timing of toxic gasesconcentrations. These units often run proprietary software algorithms.

All detectors of toxic gases, such as smoke, CO, propane, etc monitorthe quality of the air by using a dedicated sensor. Each type of sensormay have a different structure and use a different mechanism to react todifferent gases. For illustrative purposes, CO sensors are described.

There are several known detection mechanisms for toxic gases that alarmin case that the level of the gas being sampled exceeds a predeterminedthreshold. This is the typical CO or smoke detector. Once the thresholdis exceeded an audible or visual alarm (or both) will be activated.There are also devices that will trigger auxiliary devices too, but theyall fail in showing how to interface and effectively shut down the gasengine while eliminating changes to the engine itself.

One aspect of embodiments of the invention is the logic of detecting andshutting down the engine or appliance generating the toxic gas.Conventional detectors may alarm or trigger only if toxic levels aredetected. In embodiments of this invention, the device or appliance willwork only in the absence of the toxic gas. Thus, the ignition mechanismwill only be active if there is no toxic level of gas detected, asopposed to actuating a shutdown mechanism if toxic levels are detected.The engine (in the case of power generator) will not be able to bestarted if the safety unit is malfunctioning, or disconnected, or thebatteries powering the safety device and or gas detector are removed.

Power generators will generate power once they are started. Embodimentsof this invention use the power generated by the generator to power theelectronic control, sensor, circuitry, safety shutdown, etc. In order touse this approach, the engine will have to be able to be started. Oncestarted, the generator will generate power to power the CO detector andinterrupt mechanism. This means that before the engine is started, thesafety detection circuitry will not be functional, which presents aproblem.

Also, if the alternator (the unit that generates the power) is faulty,for example due to a tripped fuse, or a bad/open/shorted winding, thegenerator will not generate power, therefore disabling the CO detectorsafety device, allowing the engine to be run possibly with potentiallydangerous consequences, such as when run inside a residence, confinedspaces or poorly ventilated areas.

In other words, a gas powered generator that uses its self generatedpower to monitor and actuate a safety device will disable its own safetymonitoring and detection if for any reason or failure it will fail togenerate power, although the gas engine will continue to effectively runand possibly generate toxic levels of gases. Thus, the health of theelectrical power generated is monitored, and the system is shut down ifthe electrical portion fails.

Embodiments of the invention use a backup battery (similar to theelectrically powered detectors with backup batteries). This backupbattery is used to allow the engine to be started and run. Inembodiments of this invention, the generator will not be able to bestarted if high concentrations of CO are detected, or if the batteriespowering up the system are no good, or have been removed, or have beenwrongly inserted.

In embodiments of the invention, once the generator starts generatingpower, the safety device will be powered by the generator, thusconserving the batteries. Rechargeable batteries can also be used here,being recharged when the generator is running.

If the alternator fails (will not generate power), embodiments of theinvention will revert to battery backup to continue monitoring thepresence of the toxic gas(es). If the batteries don't provide power torun the safety mechanism, or it malfunctions, or the batteries areremoved during the operation of the generator, embodiments of theinvention (due to the reverse logic used here) will shut down the engineregardless of the level of gas being monitored.

Certain embodiments of the invention include a working safety device toenable the operation of the appliance, as well as a good battery. Solong as there is no power to the safety device, the appliance, or powergenerator, will not be able to be started.

In the case of a POWER SWITCH (as in the case of main switches to beused in furnace rooms, boiler rooms, etc) using embodiments of theinvention, there is no need for backup batteries, since absence of powerwill mean shutting down the appliance, such as a furnace, or heater,etc. In the case of this switch, there will be no backup battery.

If toxic levels of the monitored gas are detected, embodiments of theinvention will not only disable the cause of the toxic gas but sound anaudible alarm or flasher for the hearing impaired, so people in thevicinity of the toxic gas can move out until the room can be properlyventilated.

Carbon monoxide and toxic gas detectors have been developed, used andimproved for many years. Originally passive logic (transistors, diodesand other passive components) were used in conjunction with gas sensorsof different types as described here; buzzers, flashers and even voiceintegrated circuits to monitor, trigger and alert in case of toxicconcentrations of gas are known to the public.

Latter implementations, as presently used in residential and commercialdetection units, use microcontrollers, as taught in U.S. Pat. Nos.6,819,252 and 5,828,822 (incorporated by reference) to monitor the gassensor's unit, calculate the concentration levels and compare to apredetermined threshold level. If this threshold is exceeded, the alarmsounds. Different types of software algorithms, such as taught in U.S.Pat. No. 7,142,105 (incorporated by reference), have been developed andused. There are many different types of CO detection units in themarket. What sets them apart is the type of algorithms used in order tominimize false alarms, and trigger according to the outlines andspecifications of UL-2034 (Revision October 1998) which sets the levelof toxic and dangerous levels of carbon monoxide, as well as theresponse time of the alarm according to different concentrations.

Embodiments of this invention use existing, readily available CO, smoke,and toxic gas detectors as a building block to implement the abovesafety devices, switches, etc. Specifically, and for the purpose ofexplaining the method, an implementation of the safety unit for gaspowered generators using commercial CO detectors is described.

Embodiments of this invention use and interface to the RUN/STOP switchdiscussed above, where the ignition is shorted to ground to stop theengine. When the generator's RUN/STOP switch is on the RUN position, itis electrically open, and the engine can be started and run; when theswitch is in the STOP position, it is electrically closed; thegenerator's engine is then shut down if it was running, or it cannot bestarted if it was stopped. All the examples, implementations andexplanations below are based on this type of switch.

If this mechanism is reversed on a different type of generator (such asin order to run the generator, a set of contacts is electricallyshorted; and in order to stop the generator, the electrical path isopen), a change that may be needed in certain embodiments of theinvention is to use instead of a NORMALLY CLOSED relay (or solid staterelays (SSRs)) such as relay 1510 and SAFETY SHUTDOWN terminals T30 andT40 in FIG. 15, a NORMALLY OPEN type relay or SSR.

Embodiments of the invention detect carbon monoxide emissions whileoperating portable gas powered generators. During the reduction topractice, other embodiments and uses became apparent.

These embodiments and uses include:

-   -   1—Kerosene heaters; these portable heaters, have a mechanical        tripping mechanism that retracts the wick if a mechanical        movement or shift is detected, such as a person trying to move        the heater during combustion. By using embodiments of the        invention, the same mechanism may be tripped. The poisonous gas        can be not only CO but, for example, a low level of oxygen in        the ambient, or smoke, or a combination. This application is        discussed in more detail below.    -   2—Water heaters; detection of CO or propane gas (weather natural        or liquid) can also be implemented by using embodiments of the        invention. If the system detects an unsafe level of CO, or        propane, or any dangerous gas, or a combination, it will        automatically shutdown the gas supply to the heater. This        application is discussed in more detail below.    -   3—Heating furnaces; as in the case of the water heater, if        unsafe levels of poisonous gas(es) is (are) detected, the unit        can effectively shutdown the furnace, in this case, by        interrupting the electrical supply to the furnace. The unit can        obviously shut down the gas supply to the furnace as well, but        in this case, there is always a delay from the time the gas        supply is interrupted, to the time that the main blower is        shutdown. This is to allow the circulation of cold air thru the        heating plenum, to avoid expansion/contraction of the plenum and        early cracking. In the case of presence of a poisonous gas, it        may be undesirable to simply shutdown the gas supply, since the        gas will then be distributed thru the venting system. In this        case, it is preferred to shut down the electrical power to the        furnace, and therefore cutting immediately the circulation and        further distribution of the poisonous gas.        -   U.S. Pat. No. 6,339,379 (incorporated by reference) teaches            a carbon monoxide detector for detecting the level of carbon            monoxide in a furnace supply duct. The control unit provides            a signal to the limiting switch upon detection of a carbon            monoxide level above a pre-determined level whereby the            limiting switch is activated to shut off the furnace.            Embodiments of invention differ from this because the            electrical supply and or gas is shut down as explained            herein. Also, the unit explained herein, may be installed in            the furnace's room rather than in the furnace's supply duct.            This application is discussed in more detail below.    -   4—Gas space heaters—non-vented—as in the case of Rinnai space        heaters. These heaters do not vent the combustion gases to the        outside environment. This is also a typical application where        the heaters can be equipped with this type of safety device as        in the case of furnaces, where it is advisable to abruptly        interrupt the electrical and or gas supply to the heater in the        presence of CO or low levels of oxygen. These units are becoming        extremely popular due to its simple, “local” installation, as        opposed to central air conditioned systems; also used as        retrofits in places were originally electrical wall heaters were        installed on the early ‘70’s. This application is discussed in        more detail below.    -   5—Another excellent application is a power switch (wall switch)        which will interrupt, or “trip” upon the presence and detection        of a poisonous gas. This type of switch can then be used as the        mains supply switch for boiler rooms, furnace rooms, etc. etc.        It s important to understand that this is a straight        replacement, and can be installed by simply replacing the        typical “emergency switch” for gas and furnaces, often located        at the top of stairs in basement on in the vicinity of furnaces.        This application is discussed in more detail below.    -   6—Portable BBQ's, heaters and other appliances using gas        cylinders (bottles) that can be run inside confined spaces.        Embodiments of the invention may be used to interrupt the flow        of gas to the BBQ, heater or appliance once dangerous levels of        toxic gases are detected. The unit can be built and sold as a        retrofit kit, to be installed between the gas bottle and the gas        connector of the BBQ, heater or appliance. This application is        discussed in more detail below.

FIG. 1 shows the construction of a typical gas detection unit, (forexample a CO detector). Sensor 101 monitors the presence of a certaingas in the environment. Its current output (as explained above indetail) is proportional to the level of that gas mixed with the air.Once this current is circulated thru precision resistor 104 it is thenconverted into a voltage across it. This voltage is thereforeproportional to the level of the gas detected by sensor 101. Operationalamplifier 106 amplifies the level of this voltage to a higher voltage,so as it can be read by analog to digital converter A/D 110 (this A/Dcan be either external or internally contained in the microcontroller).In addition, operational amplifier 106 converts the high impedanceoutput of the sensor into a lower impedance so A/D 110 connection loadwon't affect the output of sensor 101. Microcontroller 120 isresponsible for monitoring the levels of gas (translated as a digitalreading from A/D outputs 110). It also monitors the presence of mainspower, as well as the health of backup battery 180. Led 130 representsGREEN LED, led 140 represents AMBER LED, led 150 represents RED LED, allto indicate certain statuses as denoted in FIG. 4. It is important tonote that these three LEDs can be combined into one or two LEDs (asindicated in FIGS. 2-3) to indicate the status of the detecting unit.Buzzer 160 is an audible device used to alert of a dangerous level oftoxic gas detected by sensor 101, as well as to indicate the presence ofmains power, low battery, and unit's malfunction. TEST/RESET pushbutton70 has a double function, as in most of the commercial CO alarm units.If the safety device is in a non-alarm mode (no dangerous levels of COdetected) depressing TEST/RESET pushbutton will cause microcontroller120 to simulate an alarm, and go into an alarm mode. If gas detector isin an alarm mode, depressing TEST/RESET pushbutton 70 causes the audiblealarm 160 to be silent, but still keeps status indicator(s) LED(s) 130,140, and 150 active.

FIG. 2 is a table showing the different situations and visual status ofa typical commercial CO detection unit, having a single LED indicator,which is usually but not necessarily red. Such type of detector ismanufactured by First Alert under model No. CO-605. Note that moreadvanced CO detectors (such as First Alert Model FCD4) may use a digitaldisplay readout but still will have at least one LED to indicate thestatus according to the status table.

FIG. 3 is a table showing the different situations and visual status ofa typical commercial CO detection unit, having two LED indicators, oneis usually but not necessarily red to indicate alarm or attentionstatuses (such as a low battery) and usually but not necessarily greenindicator to indicate the status of power, i.e. if the units isreceiving electricity from the mains.

FIG. 4 is a table showing the different situations and visual status ofa typical commercial CO detection unit, having three LED indicators, oneis usually but not necessarily red to indicate alarm or attentionstatuses (such as a low battery) and usually but not necessarily greenindicator to indicate the status of power, i.e. if the units isreceiving electricity from the mains. The third LED is usually but notnecessarily AMBER or YELLOW, and it is used to indicate when levels ofthe toxic gas are increasingly high and the detector is arming fortriggering an alarm.

By closely analyzing and comparing FIG. 2, FIG. 3 and FIG. 4 it is clearthat all possibilities in the detection and alarming of dangerous toxiclevels of CO as well as low, missing batteries, loss of electricalpower, test mode and or unit's malfunction, are covered and indicated bythe status of the column denoted as RED LED of FIGS. 3 and 4. For thecase of a single LED alarm unit, as in FIG. 2 all above cases are alsocovered by the single LED. For embodiments of the present invention,therefore, the status of this LED may be monitored and accordinglyreacted to.

FIG. 5 shows a gas detector with a plug-in replaceable sensor. COdetector 310 houses a socket where toxic gas sensor 300 plugs into. COdetector 310 has at least one LED 350 to indicate status of detector. Itmay also have two or three LEDs as explained elsewhere, and denoted asLEDs 360 and 370. Buzzer 390 is an audible alarm to indicate thepresence of high levels of toxic gases as well as low batteryindication. Flasher 395 is an option to attract attention for thehearing impaired. Detector plugs into electrical mains 355, and it has abattery backup 330 that powers the detector in case of power failures.TEST/RESET pushbutton 380 is a dual function switch. If the detector isnormally operating in a non-alarm condition, by depressing it causes thedetector to simulate a high CO or toxic gas level alarm. It also teststhe proper functioning of all the electronics. If gas detector 310 is inan alarm mode, by depressing TEST/RESET pushbutton 380 causes theaudible alarm to be silent, but still keeps status indicator(s) LED(s)350, 360, and 370 active. Note that by changing the replaceable sensor,300, different toxic gases can be detected with basically the samedetector unit 310. Similarly, multiple sensors (which may bereplaceable) may be used to detect different unsafe toxic gassituations, such as CO and ammonia, and or other toxic gases.

This plug-in sensor has electronics built-in in order to standardize itsoutput so it can be interfaced to a “common” detector base 310 havingthe same functions as outlined in FIGS. 2, 3, and 4. For example, if aCO sensor with an output of 45 nA/ppm is used (as explained above) thesensor may be built using electronics to standardize, say, to 1 Volt/ppmof CO. In a similar way, a sensor may detect another toxic gas with astandardized output of 1 Volt/ppm of that toxic gas. This way the samesafety device may be used with different sensor probes in differentapplications.

FIG. 6 shows the signals from a commercial CO detector that may be usedto interface with embodiments of the invention. Gas detector 600 is anycommercial toxic gas (such as CO) detection unit, such as and similar tothe described in FIG. 5, which has either one, two or three status LEDs.For the case of a single LED detector, alarm LED 610 will be used togenerate LED signal out 620. In the case of two or three LEDs alarmunits, the signal called “RED LED” in last column of FIG. 3 and FIG. 4is used. This signal may also be obtained from the positive terminal ofthe buzzer in the detector, or through an optocoupler physicallyattached and aligned to detect the light generated by the RED LED, orthrough an acoustic sensor that receives the noise generated by thebuzzer. Main-power-operated CO alarms may have an internal power supplysimilar to those described in FIG. 7 or FIG. 8. Signal (+) DC OUT 630,is derived from signal 730 or 780 (depending on the type of power supplyused in the specific CO detector) of the detector's internal powersupply, as well as signal GROUND 650, which is derived from signal 740or 790 (depending on the type of power supply used in the specific COdetector) of the detector's internal power supply. Signal (+) BATTERY IN640 is the positive terminal of the backup battery of the CO detector,and it can be obtained from the detector's battery holder.

For explanation purposes, two typical internal power supply topologiesused to rectify the AC mains and convert to DC to power the electronicsof the detector are shown. Other topologies exist as understood by thoseof skill in the art.

FIG. 7 is a typical internal power supply in commercial CO detectors.Transformer 700 is connected to mains power line. Low voltage side oftransformer 700 is connected to a full bridge rectifier 710 whichrectifies the AC output of transformer 700. Electrolytic capacitor 720filters the rectified DC output of bridge rectifier 710 in order toobtain a clean, low ripple DC voltage. Voltage signal 730 and groundsignal 740 can be used to interface to embodiments of the invention.

FIG. 8 is yet another typical internal power supply in some commercialCO detectors. Transformer 700 is connected to mains power line. Lowvoltage side of transformer 700 is connected to rectifier diodes 760 and770 which rectify the AC output of transformer 700. Electrolyticcapacitor 750 filters the rectified DC output in order to obtain aclean, low ripple DC voltage. Voltage signal 780 and ground signal 790can be used to interface to embodiments of the invention.

FIG. 9 is a block diagram of an embodiment of the invention, where a COdetection unit 900 has an internal or removable gas sensor 901, andplugs into main power by means of a built-in plug or terminal strip orother type of connector 905. Backup battery 950 powers the detector andelectronics when there is no power from the main (such as in the case ofthe portable generators, when the generator is not running). RED SIGNALOUT 909, (+) DC OUT 910, GROUND 911 and (+) BATTERY IN 913 are theinterface signals from/to the CO detector 900 and obtained as explainedin FIG. 6 and above. Interrupt electronics 940 contains the electronicsto analyze, properly react and activate safety relay 925 in response toRED LED signal condition as specified in FIGS. 2, 3, and 4.

Battery backup 950 runs the detector 900 as well as the electronics 940.Power switch 970 disables all the electronics and also functions as theRUN/STOP switch for the portable power generators. Safety NORMALLYCLOSED (NC) relay 925 is normally de-energized, and therefore NORMALLYCLOSED contacts 930 are shorted when there is no power to the system.

Portable gas power generators often use a switch that normally lets thegas engine run when the contacts of this switch are open. In otherwords, to start the engine the switch needs to be electrically open, andto shut down the engine, it shorts the two wires, or, as in most if notall the portable generators in the market, to ground, or frame ground(the metal frame where the generator is housed). Embodiments of theinvention replace (or connect in parallel, as shown later) the RUN/STOPswitch by means of contact 930 in safety relay 925 thru electrical wires940. Note than in the case of a safety switch, for example in afurnace's safety switches, this contact can be normally open and whenthe relay is energized, the contacts are closed, enabling the flow ofelectricity to the furnace, boiler room or other such systems asunderstood by those of skill in the art.

FIG. 10 shows how an embodiment of the invention interfaces to aportable power generator 1000. Portable power generators have a RUN/STOPbuilt in switch 1010. This switch, when open (RUN position), lets thegas engine run by enabling the ignition module of the gas engine to run.When shorted to ground, the engine stops (STOP position). The operationof ignition module of the gas powered engines may be any module operablein this configuration.

By simply connecting SAFETY SHUTDOWN contacts 930 in FIG. 9 in parallelto RUN/STOP switch 1010 (thru electrical wires 940) the operation of thegas engine may be controlled externally. RUN/STOP switch 1010 is thusleft open (RUN position on the generator), disconnected or totallyremoved, since now power switch 970 of FIG. 9 will now control theRUN/STOP function.

It is important to note that in many portable power generators, one leadof the RUN/STOP switch 1010 is connected to the main frame of the powergenerator 1000, which is also electrically connected to the ground ofalternator 1050, forming a GROUND connecting point 1060. In this case,the interfacing of embodiments of the invention to the generator is evensimpler, by connecting to the main frame (ground) and the other lead tothe ignition module. So, embodiments of the invention connects the powergenerator to the main, ground, and RUN/STOP signal.

FIG. 11 is a representation of an embodiment of the invention using anelectromechanical relay and active logic. This system was successfullyinterfaced to a commercial CO detector made by First Alert Model CO-605.This is one of the newest units in the market which plugs into the powermains and also has a battery backup using 2 AA type batteries, for atotal of 3 Volts. Most of the CO detectors of this type in the markettoday use a 9 Volt battery. These 9 Volt batteries have a tendency todischarge faster than the AA or AAA types. An implementation tointerface to a 9V battery backed up system is described below. It isalso possible to implement the safety device by using a microcontrollerwith built-in (firmware) software. Referring to FIG. 11, batteries BT1,BT2, BT3, and BT4 are 1.5 Volt batteries. Switch SW1, being a DPDT typehas two sections SW1A and SW1B. Batteries BT1 and BT2 are used to powerup the backup section of the CO detector (total of 3 Volts) thruRUN/STOP switch SW1A (this is also the switch that will manually controlthe ignition and shutdown of the power generator). Note that when switchSW1A is OFF, power for the CO detector is interrupted. Therefore, therewill be no drain to the batteries. Batteries BT1, BT2, BT3 and BT4 forma 6 volts supply to the electronics of the shutdown mechanism. Safetyshutdown terminal T1 and safety shutdown terminal T2 are connected inparallel to the RUN/STOP switch of the power generator (switch 1010 inFIG. 10) as explained elsewhere. Switch 1010 is either disconnected andremoved, or left in the ON position as explained above (so the enginecan be run).

When the generator is not running, the CO detector unit will not receivepower thru its main power terminals. Upon closure of SW1A, CO detectoris energized. Most of the commercial detectors, upon insertion of thebatteries (or in this case upon switching switch SW1A to ON position)the RED LED will briefly light up (alarm) as a self test. In order toavoid this blink to trigger the safety mechanism of embodiments of theinvention, time constant given by C1 and R5 will hold “D” type flip-flopU1A on reset, and consequently negated output Qnot (Qnot means thelogically inverted output of Q. If Q=H then Qnot=L, and if Q=L thenQnot=H. H means a logical HIGH and L means a logical LOW) of flip-flopU1A (pin 2 of U1A) will be in a high state, energizing relay LS1 thrudiode D3, current limiting resistor R4, and buffer transistor Q3. Thistiming constant T=R5×C1 is long enough for the CO detector to finish theself test. Once relay LS 1 is energized, electrical contact betweenterminals T1 and T2 will be open, as well as the electrical path thruSW1B (since switch SW1 is in the RUN position), effectively enabling tostart the gas engine of the generator. Transistor Q2, current limitingresistor R2, optical isolator ISO1, triac Q1 and resistor R1 form anisolated redundant electronic relay, or solid state relay (SSR). OutputQ of flip flop U1A (pin 1 of U1A) is low due to the reset issued asexplained above. Q2 is then in a non conductive state, as well as lightemitting diode of ISO1, therefore holding triac Q1 also in a nonconductive state. The electrical path between T1 and T2 is thereforeopen. Note that terminals MT1 and MT2 of triac Q1 are electricallyconnected in parallel to the normally closed contacts ofelectromechanical relay LS1. Diode D2 protects transistor Q3 fromdamaging reverse voltage when coil of relay LS 1 is de-energized. LED D1and resistor R3 indicates the status of the safety shutdown unit. If theLED is ON, the engine can be started. Clock input CLK to flip-flop U1Ais low since RED LED indicator is OFF under normal operatingcircumstances. It is also weakly held down by pull-down resistor R6.Once the gas engine is started (manually, by means of a cranking batteryor other electrically cranking, or by other means, depending on the typeof power generator) the CO detector will receive main power (which couldbe 120 Volts or 220 volts) from the generator, and therefore the COdetector will revert to AC operation, conserving batteries.

The (+) DC OUT (i.e., the signal from power supply outputs 730 and 780in FIG. 7 and FIG. 8) is now active, and reaches the input to linearregulator U2. Output of linear regulator U2 is around 6 volts, and afterdiode D4 will be around 5.7 volts (forward voltage of a schottky diode).This voltage is higher than the sum of battery voltages sum BT1, BT2,BT3 and BT4 (around 6 volts), less the voltage drop of around 1.4 voltsthru series diodes D5 and D6. Since output voltage at the cathode of D4(around 5.7 volts) is higher than voltage at cathode of D5 if no mainvoltage was present (around 4.6 volts), the safety circuit will bepowered from the generator's main and not from batteries. At this point,the current drain from the batteries will be of that needed by the COdetector to check for a “low battery” condition. Capacitor C3 is used asadditional DC filtering, and to clean up spikes.

If carbon monoxide raises to toxic levels in the environment, for anyreason, the RED LED SIGNAL OUT of the detector will go high (caused byeither a flashing LED or a constant ON RED LED signal, as explained inFIGS. 2, 3 and 4), causing output of flip flop U1A, Qnot, to go low, aswell as Q output of flip-flop U1A to go high. As output Q of flip-flopU1A goes high, optoisolator ISO1 will conduct (LED energized by Q2)effectively putting the triac Q1 into conduction, and therefore shortingSAFETY SHUTDOWN terminals T1 and T2. At this point the engine will stoprunning. And flip-flop U1A output Qnot is now low. D3 is then no longerconducting, and transistor Q3 will stop conducting after time constant(dependent on R4 and C2) falls below approximately 0.7 Volts. This willthen de-energize relay LS1, shorting also terminals T1 and T2, inparallel to already conducting triac Q1. This is done for one or more ofthe following reasons: (1) Q1 will short terminals T1 and T2 earlierthan the contacts of relay LS1 (which will short after a given timeconstant R4×2) to preserve the relay's contact from arching and wearingout, and (2) for redundancy purposes, if Q1 fails in shutting down theengine, LS1 will do it.

Note that a low battery warning indication will cause the RED LED alsoto blink (this is normally done at a rate of one blip per minute) whichwill also cause the system to shutdown.

It is desirable that the safety shutdown system work even in the absenceof power generated by the alternator's generator. If for some unusualreason the alternator goes bad (for example by an internal short of thewindings) or because of a tripped fuse, or a cut wire, then the safetydetection unit will continue to monitor for the presence of CO, and itwill shut down the gas engine as a safety precaution if the batteriesare low or there is no power received from the generator. On the sameprinciple, if the batteries are removed by the user, and the samefailure occurs (the generator will stop generating power) the systemwill immediately shut down due to the lack of power to hold relay LS1with the contacts open. The same mechanism applies when the TEST/RESETbutton is actuated in the CO detector. An alarm status will be issued,triggering exactly the same mechanism as explained above. Since thissystem is intended to save lives, redundancy and possible scenariosknows to the inventor were considered.

When the system is running normally, with good batteries and with thegenerator generating power, by switching RUN/STOP switch SW1 to STOP orOFF position, power will be interrupted to the safety system, but beforerelay LS1 is de-energized (due to residual power in the system) switchSW1B (which is mechanically actuated simultaneously to SW1A) will shortcircuit terminals T1 and T2 effectively shutting down the gas enginefurther preserving the contacts of relay LS1. It is also important tounderstand that without batteries, the power generator will not be ableto be started up. This is also a safety design consideration. If thepower generator was allowed to be started in the absence of power, andthe alternator went bad, the CO detector and safety unit will not beable to distinguish the difference between a non running generatortrying to be started, or a running generator with a bad alternator,allowing the unit to be run even in the presence of dangerous levels ofCO. Another embodiment of the invention includes a mechanically timedswitch (described below) which will allow the engine to be started untilpower is generated. Using this type of switch, the CO detector will neednot to have backup batteries, although the unit as described, withbackup battery, is much safer. It is also important to understand thatif the generator is shutdown by the safety system described herein, andswitch SW1 is not turned off, the CO detector will audibly alerts theoccupants that dangerous levels of CO caused the gas engine to be shutdown. The unit will, indeed not only shut down but wake up the occupantsto alert of a potentially lethal situation. In an embodiment with amechanical timed switch, although the generator will be shut down andprevented from generating more CO, it may not alert the occupants ofsuch a dangerous situation.

FIG. 12 shows a similar implementation, this time using a commercial COdetector with a 9 Volt battery. This is another representation of anembodiment of the invention using an electromechanical relay and activelogic. This system was successfully interfaced to a commercial COdetector made by First Alert. As above, it is possible to implement thesafety device using a microcontroller with built-in software (i.e.firmware). Referring to FIG. 12, switch SW11, being a DPDT type has twosections SW11A and SW11B. Battery BT11, is a 9 Volt battery used topower up the backup section of the CO detector thru RUN/STOP switchSW11A (this is also the switch that will manually control the ignitionand shutdown of the power generator). Note that when switch SW11A is inthe STOP or OFF position, power for the CO detector is also cut down.Therefore, there will be no drain to the battery. Battery BT11 alsopowers the electronics of the shutdown mechanism. Safety shutdownterminal T11 and safety shutdown terminal T12 are connected in parallelto the RUN/STOP switch of the power generator (switch 1010 in FIG. 10).Switch 1010 is either disconnected and removed, or left in the ONposition as explained above (so the engine can be run).

When the generator is not running, the CO detector unit will not receivepower thru its mains power terminals. Upon closure of SW11A, CO detectoris energized. Most of the commercial detectors, upon insertion of thebatteries (or in this case upon switching switch SW11A to ON) willbriefly light up the RED LED (alarm) as a self test. In order to avoidthis blink to trigger the safety mechanism embodiment of the invention,time constant given by C11 and R15 will hold “D” type flip-flop U11A onreset, and consequently negated output Qnot of U11A (pin 2) will be in ahigh state, energizing relay LS11 thru current limiting resistor R14,and buffer transistor Q13. This timing constant T=R15×C11 is long enoughfor the CO detector to finish the self test. Once relay LS11 isenergized, electrical contact between terminals T11 and T12 will beopen, as well as the electrical path thru SW11B (since switch SW11 is inthe RUN position), effectively enabling to start the gas engine of thegenerator. Transistor Q12, optical isolator ISO11, triac Q11 andresistor R11 form an isolated redundant electronic relay, or solid staterelay (SSR). Output Q of flip flop U11A (pin1) is low due to the resetissued as explained above. Q12 is then in a non conductive state, aswell as light emitting diode of ISOM therefore holding triac Q11 also ina non conductive state. The electrical path between T11 and T12 is alsoopen. Note that terminals MT1 and MT2 of triac Q11 are electricallyconnected in parallel to the normally closed contacts ofelectromechanical relay LS11. Diode D12 protects transistor Q13 fromdamaging reverse voltage when coil of relay LS11 is de-energized. LEDD11 and resistor R13 indicates the status of the safety shutdown unit.If the LED is ON, the engine can be started. Clock input CLK toflip-flop U11A is held down by pull down resistor R16. Once the gasengine is started the CO detector will receive main power from thegenerator (which could be 120 volts or 220 volts) and therefore the COdetector will revert to AC operation.

The (+) DC OUT (i.e., signal from power supply output's 730 and 780 inFIG. 7 and FIG. 8) is now active, and reaches the input to linearregulator U12. Output of linear regulator U12 is around 10 volts, andafter diode D14 will be around 9.7 volts. This voltage is higher thanbattery voltage BT11 (around 9 volts) less the voltage drop of around0.7 volts thru series diode D15. Since output voltage at the cathode ofD14 (around 9.7 volts) is higher than voltage at cathode of D15 if nomains voltage was present (around 8.3), the safety circuit will bepowered from the generator's main and not from batteries. At this point,the only current drain from the batteries will be of that needed by theCO detector to check for a “low battery” condition. Capacitor C13 isused as additional DC filtering, and to clean up spikes.

If carbon monoxide concentration rises to toxic levels in theenvironment, for any reason, the RED LED SIGNAL OUT of the detector willgo high (caused by either a flashing LED or a constant ON RED LEDsignal, as explained in FIGS. 2, 3 and 4), causing output of flip flopU11A, Qnot, to go low, as well as Q output of flip-flop U11A to go high.As output Q of flip-flop U11A goes high, optoisolator ISO11 will conduct(LED energized by Q12) effectively putting the triac Q11 intoconduction, and therefore shorting SAFETY SHUTDOWN terminals T11 andT12. At this point the engine will stop running, and flip-flop U11Aoutput Qnot is now low. D13 is then no longer conducting, and transistorQ13 will stop conducting after time constant given by R14 and C12 fallsbelow approximately 0.7 Volts. This will then de-energized relay LS11,shorting also terminals T11 and T12, in parallel to already conductingtriac Q11. This is done for two reasons: (1) Q11 will short terminalsT11 and T12 earlier than the contacts of relay LS11 (which will shortafter a given time constant R14×C12) to preserve the relay's contactfrom arching and wearing out, and (2) for redundancy purposes, if Q11fails in shutting down the engine, LS11 will do it. Note that a lowbattery will cause the RED LED also to blink (this is normally done at arate of one blip per minute) which will also cause the system toshutdown. The same mechanism applies when the TEST/RESET button isactuated in the CO detector. An alarm status will be issued, triggeringexactly the same mechanism as explained above.

When the system is running normally, with good batteries and with thegenerator generating power, by switching RUN/STOP switch SW11 to the OFFposition, power will be interrupted to the safety system, but beforerelay LS11 is de-energized (due to residual power in the system) switchSW11B (which is mechanically actuated simultaneously to SW11A) willshort circuit terminals T11 and T12 effectively shutting down the gasengine further preserving the contacts of relay LS11. It is alsoimportant to understand that without batteries, the power generator willnot be able to be started up. This is also a safety designconsideration. If the system was allowed to be started in the absence ofpower, and the alternator went bad, the CO detector and safety unit willnot be able to distinguish the difference between a non runninggenerator trying to be started, or a running generator with a badalternator, allowing the unit to be run even in the presence ofdangerous levels of CO.

FIG. 13 shows yet another embodiment of the invention which also uses acommercial CO detector but does not use an electromechanical relay, butrather an implementation of a normally closed solid state relay (SSR).This type of SSR will present a short on the terminals of the triac, foras long as there is no power applied to the circuit, therefore achievingexactly the same results of the “inversed logic” (i.e., “do not allow tostart the engine until the safety unit is powered up and running”). Thiscircuit can be used for any CO detector using any type of batteries(such as 9V or 1.5V or any combination of them). Since the electroniccircuit operates exactly as described already in FIGS. 11 and 12, onlythe implementation of the normally closed SSR is explained below.

Referring to FIG. 13, U22 regulator LM78XX is chosen to regulate outputvoltage to around 2 Volts over the battery's BT21 voltage used in thedetector. For example, if the detector uses two 1.5V batteries for atotal of 3V, the regulator will be for 5 Volts. In such a case, a LM7805may be used. In this embodiment of the invention, and for simplicityreasons, we eliminated redundancy of the mechanical relay. Note thatsince a normally closed solid state relay (NC SSR) is electronicallyimplemented, the safety device will still disable the ignition of theengine even in absence of power (from the generator and/or battery BT21)to power the safety device and or the CO detector.

The combination of diodes D20, D26, D27, D28, D29, capacitor C24, triacQ21, and isolator ISO21 form an all solid state, optocoupled, normallyclosed switch circuit (or NC SSR). One portion of this static switch isa clamping device to turn off/eliminate gate drive and maintain very lowpower dissipation through the clamping component in addition to havinglow bypass leakage around the power triac device. In selecting the powertriac for load requirements, gate sensitivity may be chosen to maintainlow power requirements. Switch SW21, being a DPDT type has two sectionsSW21A and SW21B. Battery BT21, is used to power up the backup section ofthe CO detector thru RUN/STOP switch SW21A (this is also the switch thatwill manually control the ignition and shutdown of the power generator).Note that when switch SW21A is in the STOP or OFF position, power forthe CO detector is also interrupted. Therefore, there will be no drainto the battery. Battery BT21 also powers the electronics of the shutdownmechanism. Safety shutdown terminal T21 and safety shutdown terminal T22are connected in parallel to the RUN/STOP switch of the power generator(switch 1010 in FIG. 10). Switch 1010 is either disconnected andremoved, or left in the ON position as explained above (so the enginecan be run).

When the generator is not running, the CO detector unit will not receivepower thru its mains power terminals. Upon closure of SW21A, CO detectoris energized. Most of the commercial detectors, upon insertion of thebatteries (or in this case upon switching switch SW21A to ON) willbriefly light up the RED LED (alarm) as a self test. In order to avoidthis blink to trigger the safety mechanism embodiment of the invention,time constant given by C21 and R25 (timing constant T=R25×C21 is longenough for the CO detector to finish the self test) will hold “D” typeflip-flop U21A on reset, and consequently negated output Qnot of U21A(pin 2) will be in a high state, energizing optocoupler ISO21 whichcontrols the NC SSR (formed by D20, D26, D27, D28, D29, C24, R21 and Q21as explained above) via Q23 and R27.

Cathodes of D28 and D29 are then shorted thru ISO21 to the anodes of D26and D27, which then causes Q21 to be open, and therefore SAFETY SHUTDOWNterminals T21 and T22 to be open, effectively allowing the gas poweredengine of the generator to run. Note that T21 and T22 will be also openthru SW21B (since switch SW21 is in the RUN position). LED D21 andresistor R23 indicates the status of the safety shutdown unit. If theLED is ON, the engine can be started. Clock input CLK to flip-flop U21Ais held down by pull down resistor R26. Once the gas engine is startedthe CO detector will receive main power from the generator (which couldbe 120 volts or 220 volts) and therefore the CO detector will revert toAC operation.

The (+) DC OUT (i.e., signal from power supply output's 730 and 780 inFIG. 7 and FIG. 8) is now active, and reaches the input to linearregulator U22. Output of linear regulator U22 is higher than batteryvoltage BT21 since we have chosen U22 for that reason. Since outputvoltage at the cathode of D24 is higher than voltage at cathode of D25if no mains voltage was present, the safety circuit will be powered fromthe generator's main and not from batteries. At this point, the onlycurrent drain from the batteries will be of that needed by the COdetector to check for a “low battery” condition. Capacitor C23 is usedas additional DC filtering, and to clean up spikes.

If toxic CO levels cause to trigger the CO detector, or power is removedto the detector whether due to its main supply being interrupted, or byremoval of the CO detector's battery(ies), U21A's Qnot output will golow. Q23 will then be in a non conductive state, turning OFF internalLED of ISO21 causing its internal NPN output transistor to go into anopen state. Bridge rectifier formed by diodes D26, D27, D28, and D29will then cause triac Q21 to go into conduction mode effectivelyshorting SAFETY SHUTDOWN terminals T21 and T22, causing the gas engineto shutdown. This is one implementation of a normally closed SSR, andthere are many other obvious to persons skilled in the art.

FIG. 14 shows yet another implementation using the already-existingmicro processor (microcontroller) built in and running theabove-explained commercial type CO detector and alarm unit. For thisexample, a normally closed solid state relay (NC SSR) is used, asexplained for the circuit in FIG. 13, for example. Note that this couldalso be replaced by a normally closed electromechanical type relay. Inthis implementation, and taking advantage of the microcontroller, themanufacturer of the CO alarm or detector will only need to include theelectronics (or electromechanical relay) of a NC SSR and a software coderoutine may be combined to implement of a “D” type flip-flop similar tothe hardware implementation and function of U1A in FIG. 11 withnecessary delay upon power up or insertion of backup batteries in ordernot to trigger the SSR. Microcontroller 1420 polls the CO sensor 1410,and upon determination of dangerous levels of CO (based on algorithmssuch as the one taught in U.S. Pat. No. 7,142,105, incorporated byreference) it will accordingly indicate RED, GREEN, and AMBER LEDs 1400(or at least one LED) with similar status indication as explained inFIGS. 2-4, as well as audible alarm or buzzer 1480. Output port 1485from microcontroller 1420 is used as a control signal for NC SSR (orelectromechanical relay) 1450. If control signal 1485 is high, thenSAFETY SHUTDOWN TERMINALS T50 and T60 will be on an electrically openstate. Once these terminals are connected in parallel to RUN/STOP switchof power generator as described herein (e.g. FIG. 16) they will controlthe gas engine of power generator 1600. If dangerous levels of CO aredetected, or TEST switch 1490 of CO detector is used to test the unit,or backup batteries 1496 are low or removed, or power supply 1430 loosespower due to a faulty generator, or any combination of these situations,will cause microcontroller 1420 to take output pin 1485 low, causing theNC SSR 1450 to go into a normally closed state, shutting down the gasengine.

Note that complete loss of power by a faulty alternator and removal ofbackup batteries, or tampering with the unit, to embodiments of theinvention, will cause the NC SSR to shutdown the engine. Power supply1430 and backup battery 1496 power the electronics of the CO detector.

FIG. 15 shows yet another implementation in which a commercial COdetector without a battery backup may be used and without compromisingthe safety logic described herein. Since a safety mechanism using anormally closed relay (weather electromechanical or electronic as in thecase of a SSR) in absence of power will keep the generator in a STOPstate, preventing it from being started, a temporary means is needed toallow the generator to be started up, until it starts generating enoughpower to power up the electronics of the safety device and CO detector,and then maintain the electromechanical relay or SSR in an energizedstate, thus allowing the gas engine to be run or kept running. Safetydevice 1500 comprising a CO detector and associated safety interruptcircuitry as explained in different implementations above, is connectedand powered by power outlet 1550 in power generator 1540. Contact 1520of electromechanical relay. 1510 (can be also a NC SSR) is a normallyclosed contact. When the coil of relay 1510 is not energized, contact1520 is shorted. Manual switch 1530 is a normally closed momentary OFFelectromechanical pushbutton switch; on its simplest implementation,this switch is electrically open for as long as the pushbutton isdepressed.

When the gas powered generator is not running, then there is no powersupplied to safety device 1500, and therefore there is no power toenergize relay 1510, causing electrical path between T30 and T40 to beshorted. Since SAFETY SHUTDOWN terminals T30 and T40 are connected inparallel to RUN/STOP switch 1560 of gas powered generator 1540, thegenerator cannot be started. In order to start the generator, momentaryOFF switch 1530 needs to be depressed by hand and then the enginestarted. Once the engine has been started, generator 1540 will powersafety device's circuitry 1500 (thru power outlet 1550), which in turn,and under normal operating conditions, will energize relay 1510; relay'scontact 1520 will then be open due to relay 1510 being energized,interrupting the electrical path between terminals T30 and T40 andallowing the gas engine to continue running. At this point, and once theengine has started, manual pushbutton 1530 needs not to be depressed anylonger. If toxic levels of CO are detected, safety device 1500 willde-energize relay 1510 as explained in other implementations of thesafety device; the relay's switch 1520 will now be shorted, shortingterminals T30 and T40 (thru normally closed manual switch 1530) which inturn will shutdown the gas engine. Similarly, if TEST button 1580 in theCO detector is depressed, a gas engine's shutdown will be accomplished.TEST button 1580 (on internal CO detector) mimics a high level of CO.TEST button 1580 will now be used as the STOP button to shut down theengine. Each time the engine will be shut down thru the TEST button, thesafety device will also be tested.

In another scenario, if generator's alternator fails for any reason,regardless of the CO concentration present on the ambient, power tosafety device 1500 will be interrupted, de-energizing relay 1510 andrepeating the gas engine's shutdown as explained above. This is yetanother safety net in case that the power to the safety device isinterrupted, disabling the safety interrupt device and CO detector.

Another embodiment may include a ‘timed” mechanical switch, similar tothose used in hot tubs, or attic fans. This switch 1530 once pushed (orrotated, depending on the type chosen) will momentary open theelectrical path for a fixed amount of time, say for example 15 seconds.Within this time window, the engine can then be started. Upon theexpiration of this mechanical timer, in this example 15 seconds, theswitch will return to its normally shorted position. This will free theuser both hands to start up the gas engine. If more time is needed afterthe initial mechanical timeout expired, an additional actuation of thetimed switch will give an extra 15 seconds.

FIG. 16 is a block diagram showing the way to connect embodiments of theinvention to a generator, such as within a new power generator, or for aretrofit kit for existing power generators. Gas powered generator 1600may be any type, including battery start (battery crank up type) ormanual start (“pull rope” type). Power outlet 1630 supplies power frompower generator 1600. RUN/STOP switch 1620 is the switch that enables tostart the gas engine or shuts down the gas engine (if it was running).One way that this switch may be internally connected is one lead 16200connected to metal frame of generator 1600 which is also electricallyconnected to the ground of the alternator and ground 16100 of poweroutlet 1630. Safety device 1640 receives power from generator thru powerplug 1665 once plugged into generator's power outlet 1630. Power outlet1660 is wired in parallel to power plug 1665 thru a proper wire gage tosupport the maximum current supplied by the generator 1600. Appliancesthat were previously plugged into generator's power outlet 1630 will nowbe plugged into power outlet 1660. SAFETY SHUTDOWN signal T16 is wiredto ground pins of power plug 1665 and power outlet 1460; signal T26 1680is the only electrical connection that may be made to the generator inaddition to plugging in power plug 1665 to power outlet 1630. In allcommercial generators, this is a readily and accessible wire (normallyyellow or black in color), and quick connect solder less terminals canbe used to effectively make this electrical connection, shown as 1680.If the safety system shuts down due to a detected toxic level of CO, orlow backup batteries, or any other reason as explained herein, SAFETYSHUTDOWN terminals T16 and T26 will be shorted, effectively shuttingdown the gas engine.

Existing commercial generators also may have a “low oil’ normally openswitch attached to the oil pan of the gas engine. This is another pointof connection that may be effectively used to shut down the gas engine.This wire is typically black or yellow in color in most of the powergenerators, and it is also easily accessible, since the oil pan isalways visible at the bottom of the power generator's frame.

FIG. 17 shows one implementation of an embodiment of the invention byusing the simplest commercial available CO detector in the market. Asafety device of this type may use this CO detector or it may bemanufactured as a whole unit. The possible advantages of this type ofsafety device are:

-   -   (a) It may not need to be powered by the generator, making its        installation in new portable power generators or retrofit of        existing generators easier.    -   (b) Lower manufacturing cost, by eliminating extra components,        such as transformers, diodes, filtering capacitors, and        additional electronic components.    -   (c) Small physical size due to the elimination of additional        components, some of them big in size, such as the magnetic        transformer used in the mains power supply.    -   (d) A large amount of basic CO detectors exist in the commercial        market.        Possible disadvantages are:    -   (e) If the CO detector fails, it may not shut down the engine in        cases of the presence of toxic levels of CO.    -   (f) It may be possible to start the engine even if the CO        detector is faulty.    -   (g) Since the CO detector (or detection unit if the safety        device is manufactured as a whole system instead of using a        commercial CO detector) needs batteries to function, the removal        of the batteries may totally disable the safety shutdown system        allowing the power generator to run even in the presence of        toxic levels of CO    -   (h) If the batteries used to power the safety device are bad or        very low, the safety device may also be disabled, again,        allowing the power generator to be run in any condition.

Referring to FIG. 17, switch SW170, being a DPDT type has two sectionsSW170A and SW170B; it will manually control the ignition and shutdown ofthe power generator. Battery 1785, is used to power up the CO detectorand safety device thru normally open RUN/STOP switch SW170A. Note thatwhen switch SW170A is in the STOP or OFF position, power for the COdetector is interrupted. Therefore, there will be no drain to thebattery 1785. Safety shutdown terminal T100 and safety shutdown terminalT200 are connected in parallel to the RUN/STOP switch of the powergenerator, for example, of switch 1010 in FIG. 10. Switch 1010 is eitherdisconnected and removed, or left in the ON position as explained above(so the engine can be run). Normally Closed switch SW170B is alsoconnected in parallel to terminals T100 and T200. When SW170B is in theRUN mode (SW170A will then be electrically closed), terminals T100 andT200 will also be electrically open, allowing the generator to run. Whenswitch SW170B is switched to the STOP position (SW170A will nowinterrupt power to safety device and CO detector), it will shortterminals T100 and T200 effectively shutting down the engine.Microcontroller 1720 polls the CO sensor 1710, and upon determination ofdangerous levels of CO (based on algorithms such as the one taught inU.S. Pat. No. 7,142,105) it will accordingly indicate CO level andbattery status. RED LED 1740 with similar status indication as explainedin FIG. 2, as well as audible alarm or buzzer 1730. Output port 1790from microcontroller 1720 is used as a control signal to actuate anormally open (NO) electromechanical relay (or NO SSR) 1770. Note that aNO type relay is used in order to conserve the life of the battery. Innormal operating conditions, and in the absence of toxic levels of CO,control signal 1790 is low. Since NO relay 1770 is de-energized, SAFETYSHUTDOWN TERMINALS T100 and T200 are on an electrically open state.Since these terminals are connected in parallel to RUN/STOP switch ofpower generator as described elsewhere herein (i.e. FIG. 16) they willcontrol the gas engine of power generator 1600. If dangerous levels ofCO are detected, or TEST/RESET pushbutton 1765 is used to test the unit,microcontroller 1720 under software control, in addition to setting LED1740 and sounding audible alarm 1730, will set output pin 1790 high.This will cause buffer transistor 1760 thru base current limitingresistor 1750 to go into saturation, causing NO relay 1770 to beenergized. Once energized, relay contacts 1780 will present a short inSAFETY SHUTDOWN terminals T100 and T200; this electrical short will, infact, shutdown the engine. Alarm indicator LED 1740, audible buzzer1730, and relay 1770 can be returned to their normal operating conditioneither by depressing TEST/RESET pushbutton 1765 or by switching offpower to the safety device thru RUN/STOP switch SW170. Once the systemis returned to the normal non-alarm state (and by properly ventilatingthe area in case that the system detected high levels of CO), the gasengine will then be enabled to be started again.

TEST/RESET pushbutton 1765 has a double function, as in some of thecommercial CO alarm units. If the safety device is in a non-alarm mode(no dangerous levels of CO detected) by depressing TEST/RESET pushbuttonwill cause microcontroller 1720 to simulate an alarm, and go into analarm mode, and as explained above, it will also shutdown the gasengine. If the safety device was in an alarm state, depressingTEST/RESET pushbutton will disable the audible alarm, but it will notde-energize NO relay 1170, keeping the gas generator in a stopped mode.It is possible that the only way that relay 1770 may be de-energized isby ventilating the area, and letting microcontroller 1720 go into anon-alarm mode (by measuring and detecting a safe level of CO). Theadditional software functions used to actuate the relay as explainedhere are minor software additions to the existing software runningmicrocontroller 1720, are as discussed above and incorporation thealgorithms taught in U.S. Pat. No. 7,142,105 (incorporated byreference). Note that electromechanical relay 1770 and associatedcircuitry, such as 1750 and 1760 can be replaced by a solid state relay.

FIG. 18 shows the block diagram of an internal power supply to power COdetector and safety device (whether is a commercial unit or an OEM typemanufactured unit for use as a safety device as described herein); saidpower supply 180, in addition to power the safety device, it will beused to power up a battery charging circuitry 186. The safety devicedescribed here, which can be anyone of the embodiments described above,will then contain rechargeable batteries 185, according to the type ofCO detector used (i.e. 1.5V or 9V or a combination) which will be usedas explained herein. Furthermore, the safety device works most of thetime using the power generated by the portable gas generator.Rechargeable batteries can be of the NiCd, NiMh, SLA (sealed lead acid)or any other suitable type of battery and circuitries known to those ofskill in the art. Power supply 180, being part of the safety device andCO detector, is plugged into the power generator in a similar manner asexplained with respect to FIG. 16. When the power generator is notrunning, and as explained above, RUN/STOP switch interrupts the power tothe safety device, therefore there is no current drain from the backupbatteries. Batteries will only discharge due to their internalresistance. Once the generator is started, safety device will obtainpower from power supply 180, since the generator is generating power.Diode 183 will then be conducting, while diode 182 will be open, furtherisolating rechargeable battery(s) 185. Battery charging circuit 186 isused to charge batteries 185. CHARGE/NORMAL switch 187 is left in theclosed position when rechargeable batteries are used in the system. Thisswitch is used to disable the battery charging circuitry if therechargeable battery does not have enough power to allow the cranking ofthe power generator. If this was the case, for example after a long yearwhere the power generator was not used, by simply moving the switch tothe NORMAL position, regular alkaline or other type of non rechargeablebatteries could be used.

FIG. 19 shows an implementation of a power switch, which may bemanufactured as a retrofit or replacement switch for regular wallswitches, and it will shut down the power to the appliance that is wiredto that switch in case toxic levels of gas (such as CO) is detected.

This switch can be used, for example, to replace the commonly usedswitch denoted as “EMERGENCY” in gas and oil fired furnaces. This switchis usually mandatory by the NEC (National Electrical Code) forinstallations of all furnaces. Embodiments of the invention may be builtin such a way that they may fit in commonly used electrical boxes as areplacement switch, both for existing and new constructions. Incomingpower from main 1930 is wired to normally open relay contacts 1900 ofelectromechanical relay 1920 (note that this electromechanical switchcould be a NO SSR). Main power continuously feeds power to transformer1934 regardless of relay's contacts 1900 being opened or closed. Thisguarantees that the CO detector and associated safety circuitry arepowered all the time. Transformer 1934 and power supply 1935 power theelectronics and safety device. Toxic gas detector, or CO detector 1970could be any commercial CO detector of any type as described above. LED1990 is a visual indicator or a plurality of LED's to indicate status ofCO detector 1970 according to FIGS. 2-4. Buzzer or audible indicator1980 sounds in the event of a detection of toxic levels of the gas beingmonitored. Control lines 1928 energize or de-energize coil ofelectromechanical relay 1920 in response to alarms or normal operation,functioning on a similar way to the embodiments described above. Switch1925 is used as a manual switch to turn the power feed to appliances ONor OFF in a similar way as the mechanical switch being replaced.

In normal operation, and in the absence of toxic levels of gas, relay1920 is continuously energized (provided manual ON/OFF switch 1925 iselectrically closed) thru control lines 1928 from CO detector receivingpower from power supply 1935. Contacts 1900 of electromechanical relay1920 are therefore electrically closed, providing power to the appliancethru power feed 1960 (for example a gas or oil fired furnace in aresidence). If high levels of toxic gas are detected, or the COdetector's alarm 1970 is triggered thru the TEST switch, relay 1920 willbe de-energized, effectively and immediately removing power from theappliance connected to power feed 1960. Electromechanical relay 1920will again be energized (and power restored to the appliance) only whenCO detector 1970 detects that levels of the toxic gas being monitoredhave returned to safe levels.

In normal operation conditions, manual switch 1925 will remove power torelay 1920, effectively shutting down power to the appliance, acting asa normal ON/OFF switch.

In the embodiments described above, safety device gets the main powerfrom the generator's outlet. In certain generators, where the safetydevice will be built-in, the main power may be obtained directlyanywhere within the generator itself, or by internal wiring in thecontrol panel.

In addition, it is possible to use the low voltage from the magneto of agas-engine, or for example, if another coil somewhere is wrapped in theU-shaped armature, to obtain the main power for the safety device tooperate and/or preserve the backup batteries. It is also important topoint out that many commercial generators generate 12 Volts DC, whichcan be also effectively used in any of the embodiments described, topower up the safety interrupt electronics as well as the CO detector.Such a generator is manufactured by Champion model C46535.

FIG. 20 shows an embodiment of the invention, using an electromechanicalswitch without the need for a dedicated NC relay or SSR as in the restof the implementations. This may be the most economical solution, and itmay not need the use of backup batteries for the safety device. Inessence, this is a mechanical implementation of an electronic SET/RESETtype flip-flop, where the SET function is performed manually by pushinga button, and the RESET is performed by a solenoid when the solenoidgets de-energized.

A possible disadvantage of this type of system is the fact that in orderto trip the switch and effectively shut down the generator, the safetydevice needs to have power at least once to energize the holdingsolenoid. If the alternator in the power generator is defective, and itnever generates power once it is started, the gas engine may continue togenerate toxic fumes which may reach dangerous levels. If there is nopower altogether, the CO detection system will not be able to detect thelevels of the toxic fumes and shut down the engine, in which case asafety device with battery backup may be desirable. Safety device 2000analyzes the level of toxic gas in the air, by using sensor 2030.Mechanical button 2190 of electromechanical switch 2010 is pushedmanually in order to start the engine. Once this button is pushed in,contacts 2040 of switch 2010, connected in parallel thru connection 2050to generator's RUN/STOP switch 2070, are mechanically and electricallykept in a normally open state, allowing power generator 2060 to be run(since RUN/STOP generator's switch 2070 is open or absent, as explainedherein). Once power generator 2060 is running, power generated by thealternator (or ignition system), is then used to power up safety device2000. Once powered up, safety device 2000 energizes and keeps energizedinternal solenoid 2090 of electromechanical switch 2010. The normalstate of safety device 2010 is to have solenoid 2090 energized. That is,if levels of toxic gases are safe, solenoid 2130 is kept energized.

Once levels of toxic gases reach dangerous levels, solenoid 2130 isde-energized, tripping electromechanical switch 2010, which in turn willshort normally closed contacts 2040, effectively shutting down the powergenerator 2060. Note that if for any reason the power generator stopsgenerating power, safety device 2000 will lose power, and in turn,solenoid 2090 be de-energized, again, effectively shutting down thegenerator, in this case for redundant and safety reasons. Note that allelectronic circuits used in the other embodiments described above willwork with this mechanism, in place of the NC electromechanical relay orNC SSR.

FIG. 21 shows one implementation of such electromechanical switch 2010of FIG. 20, in the de-energized position (i.e., before the generator canbe run—so power is absent). Note that this is one type ofimplementation, and persons skilled in the art may implement othertypes. Housing 2100 houses all the electromechanical components of theswitch. Knob 2190 is used to RUN and or STOP the power generator. Spring2170 returns knob 2190 to its resting position. Micro switch 2110 is anormally open switch (when not actuated its contacts 2040 areelectrically open). As shown, micro switch 2110 is actuated, andtherefore electrical connections 2040 present an electrical short.Spring 2125 returns plunger 2140 to its resting position when solenoid2130 is not energized. Plunger 2140 has a projection 2165 and a notch2135, and it is made of a magnetic material, which will cause itsretraction when solenoid 2130 is energized. Lever 2150 can rest oneither one of two stable states “A” or “B”, due to compressed spring2145 and pivoting point 2155. Shown in FIG. 21 is state “A”, which keepspressure against plunger 2140.

FIG. 23 shows lever 2150 on its stable “B” state. Spring 2145 is used tokeep lever 2150 in either one of the two states. Extension rod 2160 ofknob 2190 is used to return lever 2150 from state “B” to state “A” onceknob 2190 is pushed in. Knob 2190 is kept in place by stops 2180, whichalso limits is travel distances.

In order to start the generator, knob 2190 is pushed in (towards thehousing), causing spring 2170 to compress; it also pushes plunger 2140,compressing also spring 2125. Once notch 2135 of plunger 2140 lines upwith lever 2150 (and due to pressure caused by spring 2145 and pivotingpoint 2155), lever 2150 will hold plunger 2140 in place (as shown inFIG. 22). Spring 2125 is slightly compressed, and micro switch 2110 willnow be electrically open, presenting an electrical opening onconnections 2040.

FIG. 22 shows this state in detail (generator is ready to be started,but not started yet, and therefore safety device is not energized).Plunger 2140 is retained in position (after being manually pushed in byknob 2190) by lever 2150, which holds it mechanically locked because ofspring 2145, and pushing lever 2150 around its pivoting point 2155 (inaddition, lever 2150 “jams” plunger 2140 due to tension in springs 2125and 2170). Plunger 2140 is now compressing spring 2125, and alsoreleasing micro switch 2110, which in turn (since it is a normally OPENswitch) allows the generator to be started. Note that if lever 2150 waspreviously in state “B” (not ready to hold plunger 2140 in place thrunotch 2135), by depressing knob 2190 to the RUN position, it will changelever 2150 to state “A” by means of push rod 2160. Now, the generatorcan be cranked up (manually or electrically). Once cranked up, thegenerator will now generate power.

FIG. 23 shows the state of the switch while the generator is running.Once the generator started to generate power (thru the alternator orignition system), it will power safety device 2000, and thereforeelectromechanical switch 2010 as explained with respect to FIG. 20.

In this state, safety device 2000 energizes solenoid 2130 thruelectrical connections 2005 when the safety device is not detecting highlevel of toxic gases. Due to its receiving power, solenoid 2130 pullsferromagnetic plunger 2140, and projection 2165 pushes down lever 2150to stable state “B.” Stable state “B” is as shown in this figure. Lever2150 is held in state “B” due to spring 2145 and pivoting point 2155 oflever. Spring 2125 was also further compressed. In this state, andbecause of lever 2150 being in state “B,” de-energizing solenoid 2130will cause (because of compressed spring 2125) plunger 2140 to returnimmediately to (due to lack of magnetic pull from solenoid 2130) to itsoriginal state, further pressing micro switch 2110, and closingelectrical path thru electrical connections 2130. Once this electricalpath is closed, the generator's engine will be shut down. De-energizingthe solenoid is caused either by a high level of toxic gases detectedand proper reaction of safety device 2000, shutting down the gas engine,or by a problem with the generator stopping to generate power. This isan additional safety feature, which will shut down the engine in casethat the generator will stop generating power. If everything is normallyoperating, such as no high levels of toxic gases, generator is fullyfunctional, etc, then solenoid 2130 will be continuously energized. Notethat once solenoid 2130 is de-energized as explained above, return ofplunger 2140 to its resting position will also push outwards knob 2190to its “STOP” state. Under normal operating conditions, and withsolenoid 2130 energized, (generator is running) by pulling on knob 2190(away from housing 2100), plunger will be released from its magneticallypulled state, and micro switch 2110 will be pushed, initiating agenerator shutdown as explained above. This is the manual STOP function,implemented pulling of knob 2190.

FIG. 24 shows how to generate power for the safety device from themagneto (or generator) used in the ignition system of a typical smallgas engine. It may be convenient to power up the safety device from theignition system rather than from the power generated by the alternator.This may be the case of certain appliances, such as snow throwers, wherepower is not being generated, and a small gas engine is used.

A magneto is basically an electrical generator that has been tuned tocreate a periodic high-voltage pulse rather than continuous current. Anelectrical generator (or a magneto) is the reverse of an electromagnet.In an electromagnet there is a coil of wire around an iron bar (thearmature). When current is applied to the electromagnet's coil (e.g.with a battery), the coil creates a magnetic field in the armature. (Ina generator, the process is reversed; a magnet moves past the armatureto create electric current in the coil.) A magneto consists of thefollowing parts: An armature 2400, normally shaped like a capital “U”.The two ends of the U point toward the flywheel 2440. A primary coil2410 (which may have 200 turns) of thicker wire is wrapped around oneleg of the U. A secondary coil 2420 (which may have 20,000 turns ofthinner wire wrapped around the primary coil). An electronic controlunit that may include ignition module 2430 and/or a set of breakerpoints and a capacitor. A plurality of permanent magnets 2465 areembedded in the engine's flywheel 2440. When the magnets 2440 fly pastthe U-shaped armature 2400, they induce a magnetic field in thearmature. This field induces some small amount of current in the primarycoil 2410 and secondary coil 2420. A sufficiently high voltage should beused, so that as the magnetic field in the armature reaches its maximum,a switch in the electronic control unit 2430 opens. This switch breaksthe flow of current through the primary coil and causes a voltage spike(such as 200 volts). The secondary coil, 2420, having 100 times moreturns than the primary coil, amplifies this voltage to approximately20,000 volts, and this voltage feeds to the spark plug. By adding athird winding 2450 to the armature 2400, part of the magnetic fieldpresent in the armature, is induced into this coil, presenting analternating current AC at the output terminals of winding 2450. Byfeeding this AC voltage to full bridge rectifier formed by diodes D1,D2, D3, and D4 in diode bridge 2460, a direct current DC voltage isobtained. Capacitor 2470 is used to filter the DC voltage output bybridge 2460. Voltage regulator 2480 regulates the output DC voltage fromfull bridge to a desired voltage needed to operate the safety device.

FIG. 25 shows a safety device to alarm and control the source of toxicgases in appliances that use, for example, tanks of propane gas, such asthose used in portable space heaters, BBQs, etc. Tank of gas 2500 may bea liquefied fossil fuel, propane, or other flammable gas. When the gasin its liquefied state leaves the tank it changes into a gas state,which is used for cooking, heating, etc. These types of appliancesgenerally should not be used in confined spaces since their combustiondepletes oxygen and generates toxic gases, such as carbon monoxide. Itis an intention of this embodiment of the invention to detect, alarm,and shut down the flow of gas to the appliance in case that the levelsof toxic gases reaches dangerous levels. Gas tank 2500 connects to aflexible hose 2520 thru shut off valve 2510. The pressure inside the gastank is much higher than the pressure needed by the appliance, and alsothis pressure fluctuates depending on the volume of gas contained in thetank, being the highest when the tank is filled up to maximum capacity.Gas pressure regulator 2530 reduces high-pressure gas in a cylinder orprocess line to a lower, usable level as it passes to another piece ofequipment. It may also serve to maintain pressure within a system.However, the regulator is not a flow control device. It is used tocontrol delivery pressure only. There are three basic operatingcomponents in most regulators: a loading mechanism, a sensing element,and a control element. These three components work together toaccomplish pressure reduction. The loading mechanism determines thesetting of the regulator delivery pressure. Most regulators use a springas the loading mechanism. When the regulator hand knob is turned, thespring is compressed. The force that is placed on the spring iscommunicated to the sensing element and the control element to achievethe outlet pressure. The sensing element senses the force placed on thespring to set the delivery pressure. Most regulators use a diaphragm asthe sensing element. The diaphragms may be constructed of elastomers ormetal. The sensing element communicates this change in force to thecontrol element. The control element is a valve that actuallyaccomplishes the reduction of inlet pressure to outlet pressure. Whenthe regulator hand knob is turned, the spring (loading mechanism) iscompressed. The spring displaces the diaphragm (sensing element). Thediaphragm then pushes on the control element, causing it to move awayfrom the gas pressure regulators' seat. The orifice becomes larger inorder to provide the flow and pressure required. Safety device 2540 isplaced inline between the pressure regulator and the appliance's gasconnecting line, 2520.

FIG. 26 shows an implementation of an embodiment of the invention byusing the simplest commercial available CO detector known to theinventor in the market. A safety device of this type may use this COdetector or it may be manufactured as a whole unit. Referring to FIG.26, microcontroller 2620 polls the CO sensor 2610, and upondetermination of dangerous levels of CO (based on specific algorithms asdescribed above) it will accordingly indicate CO level and batterystatus RED LED 2640 with similar status indication as explained withrespect to FIG. 2, as well as audible alarm or buzzer 2630. Output port2690 from microcontroller 2620 is used as a control signal to actuate anormally closed (NC) electromechanical gas valve 2670. This is a gasvalve that needs a voltage pulse in order to open the flow of gas, andit is designed to draw a minimal amount of current (in order to conservethe battery of the safety device) while in the OPEN holding state. Suchtype of valves are readily available. It is important to note that inthe absence of power, whether caused by low or removed batteries, thisvalve will be normally closed and the gas flow 2600 is interrupted. Innormal operating conditions, and in the absence of toxic levels of CO,control signal 2600 is high, allowing the flow of gas thru gas pipe orhose. If dangerous levels of CO are detected, or TEST/RESET pushbutton2665 is used to test the unit, microcontroller 2620 under softwarecontrol, in addition to setting LED 2640 and sounding audible alarm2630, will set output pin 2690 low. This will cause buffer transistor2660 thru base current limiting resistor 2650 to go into a nonconducting state, causing NC gas valve 2670 to be shut off. Inembodiments of this invention, alarm indicator LED 2640, audible buzzer2630, and gas valve relay 2670 can be returned to their normal operatingcondition by depressing TEST/RESET pushbutton 2665 and by properlyventilating the area in case that the system detected high levels of CO.

TEST/RESET pushbutton 2665 has a double function, as in some of thecommercial CO alarm units. If the safety device is in a non-alarm mode(no dangerous levels of CO detected) by depressing TEST/RESET pushbuttonwill cause microcontroller 2620 to simulate an alarm, and go into analarm, as explained above; it will also shutdown the gas valve. If thesafety device was in an alarm state, depressing TEST/RESET pushbuttonwill ONLY disable the audible alarm, but it will not reopen the gasvalve. The additional software functions used to actuate theelectromechanical gas valve 2670 as explained here are minor softwareadditions to the existing software running microcontroller 2620 arediscussed above.

It will be understood that the above-described embodiments are merelyillustrative of the principles of the invention and that otherarrangements may be devised by those skilled in the art withoutdeparting from the spirit and scope of the invention.

1-60. (canceled)
 61. An electromechanical switch comprising: (a) aplunger; (b) a first switch in contact with said plunger in a firstposition of said plunger, in which a connection of said switch is open;(c) a button in sliding contact with said plunger; (d) a solenoid incontact with said plunger in a second position of said plunger, in whicha connection of said first switch is closed.
 62. The electromechanicalswitch of claim 61 further comprising a holding element in said plungerin contact with an engaging element in a third position of said plunger,in which said plunger is not in contact with said first switch and isnot in contact with said solenoid, and a connection of said first switchis closed.
 63. The electromechanical switch of claim 61 in which saidfirst switch is coupled to a relay.
 64. The electromechanical switch ofclaim 61 in which said first switch is coupled to a normally closedswitch.
 65. The electromechanical switch of claim 62 wherein saidholding element is a notch.
 66. The electromechanical switch of claim 62wherein said engaging element is a lever.